http://searchengineland.com/google-internet-stats-25578

<<Postscript: A Google UK representative answered some of my questions, clarifying the following:

   * There are no plans to launch this tool elsewhere at the moment. This is a UK-only initiative.
   * Any stats submitted by users will be verified by Google’s market research teams
   * Google license data from a number of sources, as well as bring together publicly reported facts and stats from the web (sources shown on the site)>>